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  • Conditioned reward  (2)
  • Monkey  (2)
  • 1
    ISSN: 1432-1106
    Keywords: MPTP ; Graft ; Behavior ; Parkinson's disease ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fetal substantia nigra (SN) cells were transplanted into the caudate nucleus (CN) of four vervet monkeys (Cercopithecus aethiops sabaeus) that had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP treatment appears to produce a syndrome similar to that observed in patients with idiopathic Parkinson's disease. Normal and parkinsonian behaviors were quantitated by trained observers 5 days/week. Twenty-eight behaviors based on previous factor analyses were individually scored and rated. Parkinsonian signs included freezing, head and limb tremor, difficulty in eating, delayed initiation of movement, poverty of movement, tremor that stopped with intention, decreased response to threats, and lying immobile in the cage. These signs were combined to give an overall rating of parkinsonism. A summary measure of ‘normal’ healthy behavior was also examined, including such behaviors as yawning, scratching, self-grooming, shifting, and eating. Overall ratings of parkinsonism increased and those of healthy behavior decreased after MPTP. In the 4 monkeys grafted with fetal SN cells into the CN, behavior returned to pre-treatment levels by the time of sacrifice (2, 5, or 7.5 months after grafting). Three control subjects were transplanted with either SN cells into an inappropriate brain site (cortex) or inappropriate, non-dopaminergic, cells (cerebellar) into the CN. Subjects were also compared with three control animals that did not receive MPTP but received cryopreserved or fresh SN and other cells into the CN. Only MPTP-treated subjects that received SN cells into the CN showed evidence of a reversal of the MPTP syndrome after transplantation. In addition, grafting in animals that were not MPTP-treated did not appear to affect behavior. This paper reports the specific behavioral effects of severe MPTP toxicity that were or were not reversed after transplantation and suggests that only fetal SN cells grafted into the CN may be able to reverse behavioral deficits in MPTP-treated monkeys.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Key words Compulsion ; Addiction ; Cocaine ; Amphetamine ; Cannabis ; Phencyclidine ; Nucleus accumbens ; Amygdala ; Frontal cortex ; Limbic ; Stimulus-reward association ; Conditioned reward ; Sensitization ; Drug-seeking ; Inhibitory control ; Cognition ; Conditioned stimulus ; Incentive motivational ; Dopamine ; Rat ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Drug abuse and dependence define behavioral states involving increased allocation of behavior towards drug seeking and taking at the expense of more appropriate behavioral patterns. As such, addiction can be viewed as increased control of behavior by the desired drug (due to its unconditioned, rewarding properties). It is also clear that drug-associated (conditioned) stimuli acquire heightened abilities to control behaviors. These phenomena have been linked with dopamine function within the ventral striatum and amygdala and have been described specifically in terms of motivational and incentive learning processes. New data are emerging that suggest that regions of the frontal cortex involved in inhibitory response control are directly affected by long-term exposure to drugs of abuse. The result of chronic drug use may be frontal cortical cognitive dysfunction, resulting in an inability to inhibit inappropriate unconditioned or conditioned responses elicited by drugs, by related stimuli or by internal drive states. Drug-seeking behavior may thus be due to two related phenomena: (1) augmented incentive motivational qualities of the drug and associated stimuli (due to limbic/amygdalar dysfunction) and (2) impaired inhibitory control (due to frontal cortical dysfunction). In this review, we consider the neuro-anatomical and neurochemical substrates subserving inhibitory control and motivational processes in the rodent and primate brain and their putative impact on drug seeking. The evidence for cognitive impulsivity in drug abuse associated with dysfunction of the frontostriatal system will be discussed, and an integrative hypothesis for compulsive reward-seeking in drug abuse will be presented.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Key words Locomotor activity ; Nucleus accumbens ; d-Amphetamine ; Cocaine ; Sensitization ; Conditioned reward
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The mesolimbic dopamine (DA) system has been implicated in conditioned reward (CR), locomotor sensitization, and the reinforcing properties of psychomotor stimulants. Stimuli with formerly motivationally neutral properties that gain incentive properties by their predictive association with primary reinforcers are termed conditioned, or secondary, reinforcers. In these experiments, we investigated whether cocaine sensitization could potentiate augmented responding for CR produced by intra-accumbens amphetamine. After subjects were trained on the CR paradigm for 14 days, they received a regimen of cocaine sensitization or saline injections. On 2 test days, 8–10 days later, subjects were given amphetamine (6 µg/0.5 µl) or saline infusions into the nucleus accumbens (NAc) and responding for CR was measured using the ”acquisition of a new response” paradigm. Responding on one novel lever resulted in the delivery of the conditioned stimulus (conditioned reinforcer, or CR lever), whereas responding on the other lever resulted in no CR stimulus presentation (NCR lever). Animals sensitized to cocaine showed increased responding on the CR lever after intra-NAc saline and potentiated CR lever responding after intra-NAc amphetamine. No differences in responding between the cocaine- and saline-treated groups on the NCR lever after the challenge were found. Locomotor sensitization under these conditions was confirmed in a separate group of subjects. These findings show that prior exposures to cocaine results in changes that potentiate the ability of intra-NAc amphetamine to enhance CR. Repeated stimulant drug use may induce long-term neuronal adaptations that result in increased sensitivity to the behavioral, or incentive motivational, effects of stimulant drugs.
    Type of Medium: Electronic Resource
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